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SOC > SOC Concrete > Flashcards

SOC Concrete Flashcards

1
Q
  1. What are the raw materials in Portland cement?
A 
Limestone
Cement rock
Oyster shells
Marl (Lime-rich mud-lake sediment)
Clay
Silica Sand
Iron Ore
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2
Q
  1. What is “clinkers”?
A

The raw material finely ground and carefully proportioned before heated to temperatures from 2000 to 3000 degrees (F) to form hard pellets called “Clinkers.” Cooled and then pulverized to a fine powder.

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3
Q
  1. What is air entrainment?
A

The intentional creation of tiny air bubbles in concrete

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4
Q
  1. What is the composition of concrete?
A

Mix of aggregates and entrained air held together by hardened paste made of cement and water

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5
Q
  1. What is the most commonly used cement by the military?
A

Portland cement

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6
Q
  1. What is hydration?
A

Hydration is the chemical reaction that occurs when Portland cement is mixed with water. Produces heat that causes expansion and contraction.

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7
Q
  1. What causes concrete to harden and what is the desired temperature?
A

Hydration

73 degrees

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8
Q
  1. What are the three major components of concrete?
A

Water
Aggregates
Portland Cement

(Coarse agg, fine agg, hydraulic cement, water, air)

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9
Q
  1. What are two types of aggregate
A

1) Coarse aggregate (Rock)

2) Fine aggregate (sand)

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10
Q
  1. What is aggregate?
A

It used as an inner filling material, made of sand and gravel. 60 to 80 percent of total concrete volume. Should be clean, round, hard, strong and durable.

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11
Q
  1. What is primary purpose of aggregates?
A

To gain economy

Use largest practical size to gain maximum strength

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12
Q
  1. What are the most common contaminating materials of aggregate?
A

Dirt, clay and salt

Most can be removed by washing with water

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13
Q
  1. What are the five types of Portland cement?
A 
Type I (Normal Portland)
Type ll (Modified)
Type III (High early)
Type IV (Low heat)
Type V (Sulfate Resistant)
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14
Q
  1. What is the normal cure time and some uses of Type 1 Portland cement?
A

28 days

It used for Pavement, Sidewalks, Bridges, Reservoirs, Building and etc

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15
Q
  1. What is the normal cure time and some uses of Type 2 Portland cement?
A

45 days

Large super structures, large piers, heavy abutments, heavy retaining walls

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16
Q
  1. What is the normal cure time and some uses of Type 3 Portland cement?
A

High early -7 days

Used in cold weather and high heat

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17
Q
  1. What is the normal cure time and some uses of Type 4 Portland cement?
A

Low heat -90 days

Large massive structures

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18
Q
  1. What is the normal cure time and some uses of Type 5 Portland cement?
A

Sulfate Resistant – 60 days

Used where the soil, or water, in contact with the concrete has a high sulfate content

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19
Q
  1. What types of Portland cement are air entrained?
A

Types 1, 2 and 3

Aids in freeze/thaw resistance

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20
Q
  1. What does calcium chloride do to Portland cement?
A

It accelerates both hardening and strength gain by 2% the weight of cement. Used in temps where hydration is slow
2 hours vs 6 hours

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21
Q
  1. How does Portland cement ship?
A

Bags
94lb - contain one cu ft of loose measurement

Barrels
376lb = 4 bags

Rail cars

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22
Q
  1. What is warehouse pack?
A

Sacked cement in storage packed too tightly

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23
Q
  1. What are the types of concrete?
A

Reinforced
Prestressed
Precast
Lightweight

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24
Q
  1. What is reinforced concrete?
A

Steel rods imbedded into the concrete (strong in compression, but weak in tensile strength)

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25
Q
  1. What is prestressed concrete?
A

Reinforced steel or welded wire mesh that is stretched out with tension before the concrete is poured.

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26
Q
  1. What is precast concrete?
A

Concrete cast somewhere other than its final position

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27
Q
  1. What is benefits of lightweight concrete?
A

a) In dead-loads making savings in foundations and reinforcement
b) Improved thermal properties
c) Improved fire resistance
d) Savings in transporting and handling pre-cast units on site
e) Reduction on framework and propping

28
Q
  1. What is benefits of plastic state?
A

a) Readily moldable
b) Changes shape slowly if forms are removed
c) Uniform
d) Workable nonsegregated
It can be cast or molded into nearly any size or shape

29
Q
  1. What are some advantage of concrete?
A

a) High compressive strength
b) Can be cast, molded or shaped
c) Little maintenance
d) Economical
e) Used Universally
d) Durable
e) Strength can be pre-determined

30
Q
  1. What are some disadvantage of concrete?
A

a) Low tensile strength
b) Expands and contracts
c) Shrinks when dry
d) Heavy

31
Q
  1. What is expansion and contraction?
A

Chemical reaction that occurs by moisture and temperature changes

32
Q
  1. What is the width of an expansion joint?
A

1/4 to 1/2 inch

33
Q
  1. What is the difference between construction joints and expansion joints?
A

Construction joints (Horizontal and Vertical Keyways) are not intended to allow for movement of concrete. Expansion joints and contraction joints allow for movement.

34
Q
  1. When can you place concrete underwater?
A

Placed underwater only when unavoidable.

35
Q
  1. If concrete must be placed underwater, what should the max velocity of the current be?
A

10 ft per min

36
Q
  1. When hand mixing cement, how much cement can be mixed by one man?
A

1 cubic yd per hour

37
Q
  1. When hand mixing concrete the sand, gravel and cement should be dry mixed how many times before adding water?
A

Three times

38
Q
  1. What is the formula for project volume (PV)?
A

PV = Length x Width x depth x number of structures.

• Make sure keep in feet, divide inch measurements by 12

39
Q
  1. What is the formula for Loss Factor (LF)?
A

LF = PV x LF

<5400 cu ft =1.1 or > 5400 cu ft = 1.05

40
Q
  1. What is the formula for loose volume (LV)?
A

LV = LF X 1.5

41
Q
  1. What rule do you use when calculating for materials when laying concrete?
A

1-2-3 rule

1/6 cement, 2/6 sand, and 3/6 gravel

42
Q
  1. What is the formula for convert cu ft to cu yrds?
A

Cu ft / 27 = cu yrds

43
Q
  1. When estimating for concrete work what is the rule called?
A

3/2 rule

44
Q
  1. What are forms?
A

Structures that hold concrete until sets, produces the desired shapes and sometimes surface finishes. Can represent up to 1/3 of concrete structure’s total cost.

45
Q
  1. What is essential when setting up forms?
A

Tight
Rigid
Strong

46
Q
  1. What materials can be used make forms?
A

Wood (most common and economical)
Metal
Earth
Fiber

47
Q
  1. What are the elements of wooden forms (Concrete wall)?
A 
Sheathing
Stud
Wales
Strong backs
Braces
Shoe plates
Spreaders
Tie wires
48
Q
  1. What are the elements of wooden forms (Concrete column)?
A

Sheathing
Batten
Yokes
Bracing

49
Q
  1. The rate of filling should not be exceed?
A

4 feet per hour vertically, to avoid excessive pressure on the forms, should never be dropped from greater than 3-5 feet.

50
Q
  1. What is screeding?
A

Process of stiking off the excess concrete in order to bring the surface to the right elevation

51
Q
  1. What are techniques of finishing operation?
A 
Floating - If smooth surface is required
Troweling - smoother surface is required
Brooming - If non-skid surface is required
Screeding - trimming excess off top
Vibration
52
Q
  1. What determines the strength of concrete?
A

Ratio of cement to water, less water = stronger

53
Q
  1. What are the rules of thumb for the maximum size aggregates should be in concrete?
A

The maximum size should not exceed 1/5 the minimum diameter of a wall or similar structure Not to exceed 1/3 the slab thickness Not to exceed 3⁄4 of the clear space between reinforcing bars

54
Q
  1. Where are isolation joints used?
A

where a pavement joins sidewalks and building, and intersects other pavements or bridge.

55
Q
  1. What do expansion joints do?
A

Permit volume change movement of a concrete structure or member.

56
Q
  1. how deep does the land under a slab need to be moistened?
A

6 inches

57
Q
  1. Slabs which will support load bearing walls must be what?
A

Reinforced with rebar

58
Q
  1. What is different between construction joint and Control joint?
A

1) Construction joints allow the builder to continue construction process.
2) Control joint is used at finishing state of construction. A provision for volume changes at predetermined locations that prevents a concentration of crack-producing stress forces.

59
Q
  1. What is sequence of concrete hand mixing?
A

a) Mix dry materials three times (sand, cement, and grave)

b) Add water to achieve desire concrete strength

60
Q
  1. Ingredient Equation
A 
PV = L x W x H x ( number of structure)
•	Keep measurement in feet 
Loss factor
LF= PV(1.1)         ( <5400 cu ft, add 10% (1.1)
LF= PV(1.05)      ( >5400 cu ft, add 5% (1.05)
Loose Volume 
LV= LF X 1.5  
•	LV round up to whole number
1) CEMENT 1/6 X LV = bag of cement
2) SAND 2/6 X LV = CU ft
3) Gravel 3/6 x LV = CUft
Water  Gallons = 8 x # of bag cement
If you ordering from truck,
LF = PV x (loss factor of 1.05)
YDS = LF(in CU ft) / 27
Always going to be CU yard
Only round at end
61
Q
  1. Special curing techniques
A 
1)	Hot weather
keep temperature below 90 F degree
Loosen forms ASAP
Add accelerators
Remove forms (7 days)

2) Cold weather
40 degrees F or lower
Keep concrete above 70 degrees F
Add accelerators

62
Q

What is the purpose of water in making concrete?

A

Effect hydration

Improve workability

63
Q

What are the requirements for water used in concrete?

A

It should be free of acids, alkalis, oils, and other organic impurities (excessive sulfates)

64
Q

How do you find the largest practical size for aggregate?

A

<1/5 minimum diameter of a wall
<1/3 slab thickness
<3/4 clear space between reinforcing bars

65
Q

What are the other types of cement?

A 
White Portland - Architectural
Air entrained - freeze-thaw
Oil Well - hardens at temps in deep wells
Waterproofed Portland
Plastic Cement
66
Q

Properties of desirable concrete

A

Hardened Concrete (strength determined by water content: 1 bag = 2.5 gallons)
Durability
Water-tightness

67
Q

Types of Foundations

A

Footer
Monolithic Slab
Stem Wall
Floating Slab

SOC (13 decks)

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